POS0510 INTERMITTENT FASTING REDUCES CRYSTAL-INDUCED INFLAMMATION
Authors: N. Pham, T. W. Chirayath, F. Castelli, F. Fenaille, A. L. Nguyen, F. Brial, A. Latourte, F. Lioté, P. Richette, T. Bardin, H. K. Ea
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Inflammation induced by monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals depends on interleukin (IL)-1β activated by the NLRP3 inflammasome. The inflammatory response can be modulated by diet, fasting, and caloric restriction. <h3>Objectives</h3> To determine whether intermittent fasting reduces MSU and CPP crystal-induced inflammation. <h3>Methods</h3> Crystal-induced inflammation was assessed using both types of crystals <i>in vivo</i> in the air pouch model in 8-week-old wild-type male mice fed either with a normal ad libitum diet or intermittent fasting (IF) (every over day fast, 2 days during 1 week). Inflammatory cytokine production (IL1β and CXCL-1) was assessed in the pouch lavages and the cellular infiltrate analyzed by histology (H&amp;E staining). Metabolomic analyses were performed by high-performance liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) on air pouch membrane, serum, and liver samples. Changes in metabolites associated with diet interventions were studied by the Metaboanalyst platform and we established the metabolic profiles for each experimental condition. In vitro, human monocytes THP-1 were stimulated by sterile synthetic crystals of MSU and CPP while the production of inflammatory cytokines was quantified by ELISA. To assess the role of glutamine/glutamate metabolism pathway related to IF in microcrystalline disease, the concentrations of glutamine/glutamate in synovial fluids (SF) from patients with gout, CPP-related disease and osteoarthritis (OA) were quantified by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). <h3>Results</h3> Inflammation induced by MSU and CPP crystals was drastically decreased by IF compared with normal diet: IL-1β (MSU 0.0 vs. 30.0 pg/ml; CPP 0.0 vs. 47.5 pg/ml p&lt;0.0001); CXCL-1 (MSU 67.5 vs. 186.8 pg/ml, CPP 156.1 vs. 549.5 pg/ml, p&lt;0.005); as were cell infiltration assessed by number of cells in the air pouch lavages (MSU 0.2 x 10<sup>6</sup> vs. 1.1 x 10<sup>6</sup>; CPP 0.4 x 10<sup>6</sup> vs 2.9 x 10<sup>6</sup>; p&lt;0.0001) and membrane histology semi-quantitative score (MSU 0.6 vs 3.0; CPP 0.8 vs 2.7; p&lt;0.0001). Reduction of inflammation by IF was associated with significant changes in membrane, serum and liver metabolites. IF increased ketone bodies (hydroxybutyric acid) as well as cholic acid, acetyl glycine, hydroxy caproic acid. In contrast, IF decreased carbohydrate metabolites, as well as glutamate and succinic semi-aldehyde. Many metabolic pathways were altered by IF such as galactose, starch, sucrose, aspartate, glutamate, alanine and arginine metabolism. Interestingly, the glutamine and glutamate metabolic pathway was enriched in serum, membrane and liver compartments. Glutamine/glutamate involvement in microcrystal-induced inflammation was evidenced in SFs. SF concentration of glutamine was decreased during gout and CPP flares compared to OA effusion (gout 352.3 µM and CPP 357.5 µM vs OA 509.3 µM, p&lt;0.0001 and p&lt;0.0001 respectively) while the concentration of glutamate increased in gout (gout 212.5 µM vs 58.0 µM, p&lt;0.0001; CPP 66.1 vs 58.0 µM, p=0.4). The glutamine/glutamate ratio was decreased in synovial fluids of crystal-related diseases compared to OA (gout 1.4 and CPP 6.1 vs OA 9.4, p&lt;0.0001 and p&lt;0.05 respectively). <i>In vitro</i>, crystal-induced inflammatory cytokine production was decreased by overnight serum deprivation (IL-1β: MSU 1446 vs 5464 pg/ml; CPP 3670 vs 7797 pg/ml, p&lt;0.005; TNF-α: MSU 7.0 vs 47.0 pg/ml; CPP 15.6 vs 89.3 pg/ml, p&lt;0.05; IL-8: MSU 2896 vs 9781 pg/ml; CPP 3984 vs 6820 pg/ml, p&lt;0.01). The inhibition of crystal-induced IL-1β production by serum deprivation was abrogated when cells were treated with 3-MA, an autophagy inhibitor (MSU 1446 vs 4912 pg/ml; CPP 3670 vs 9367 pg/ml, p&lt;0.005). <h3>Conclusion</h3> Intermittent fasting alleviates crystal-induced inflammation by altering many metabolic pathways, particularly those associated with glutamine and glutamate. Further studies are needed to determine how IF modulates metabolism to dampen crystal-induced inflammation. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.